Report on Soufriere Hills (United Kingdom) — 13 November-19 November 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 13 November-19 November 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Soufriere Hills (United Kingdom). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 13 November-19 November 2002. Smithsonian Institution and US Geological Survey.
16.72°N, 62.18°W; summit elev. 915 m
All times are local (unless otherwise noted)
Activity at Soufrière Hills increased slightly during 8-15 November. On the 8th and 9th pyroclastic flows traveled 900-1,000 m NW into Tyer's Ghaut at the headwaters of the Belham Valley. From the 10th to 15th, lava-dome growth and ash venting were concentrated to the NE at the base of the NW lava lobe. Rockfall and pyroclastic-flow debris were shed predominantly NE down Tar River Valley and Tuitt's Ghaut and occasionally down the NW flank. During the last 3 days of the report period, the size and energy of the pyroclastic flows increased slightly. SO2 emission rates were higher than the previous week, with a mean emission rate of 520-560 tons per day.
Geologic Background. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.